It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas, the first in the noble gas group in the periodic table. The first alloy used on a large scale was bronze, made of tin and copper, from as early as 3000 BC. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula S8. Yttrium is a chemical element with atomic number 39 which means there are 39 protons and 39 electrons in the atomic structure. It is also sometimes considered the first element of the 6th-period transition metals and is traditionally counted among the rare earth elements. Promethium is a chemical element with atomic number 61 which means there are 61 protons and 61 electrons in the atomic structure. The pair of 1s electrons are a complete shell and form the kernel of the lithium atom. Like all elements with atomic number over 100, nobelium can only be produced in particle accelerators by bombarding lighter elements with charged particles. Lithium is a chemical element with atomic number 3 which means there are 3 protons and 3 electrons in the atomic structure. It is the heaviest essential mineral nutrient. Iron is a chemical element with atomic number 26 which means there are 26 protons and 26 electrons in the atomic structure. ELECTRON CONFIGURATION: 1: Hydrogen: 1s 1: 2: Helium: 1s 2: 3: Lithium … Approximately 60–70% of thallium production is used in the electronics industry. Gadolinium is a chemical element with atomic number 64 which means there are 64 protons and 64 electrons in the atomic structure. Thus, numerical mathematical methods are required, even to solve the syst… The modern periodic law; 9. Liquid helium is an important cryogenic material and is used to study superconductivity and to create superconductive magnets. Zirconium is widely used as a cladding for nuclear reactor fuels. The electron configuration is the distribution of electrons of an atom or molecule (or other physical structure) in atomic or molecular orbitals. It is also the most corrosion-resistant metal, even at temperatures as high as 2000 °C. The chemical symbol for Neptunium is Np. The chemical symbol for Gold is Au. The chemical symbol for Selenium is Se. According to the Pauli exclusion principle, if two electrons occupy the same orbital, they must have opposite spins. Argon is mostly used as an inert shielding gas in welding and other high-temperature industrial processes where ordinarily unreactive substances become reactive; for example, an argon atmosphere is used in graphite electric furnaces to prevent the graphite from burning. Arsenic is a metalloid. Scandium is a chemical element with atomic number 21 which means there are 21 protons and 21 electrons in the atomic structure. Germanium is a chemical element with atomic number 32 which means there are 32 protons and 32 electrons in the atomic structure. The chemical symbol for Iridium is Ir. The chemical symbol for Yttrium is Y. Yttrium is a silvery-metallic transition metal chemically similar to the lanthanides and has often been classified as a “rare-earth element”. All Group 1 atoms can lose one electron to form positively charged ions. © 2019 periodic-table.org / see also Terbium is a silvery-white, rare earth metal that is malleable, ductile, and soft enough to be cut with a knife. In the perspective of quantum mechanics, helium is the second simplest atom to model, following the hydrogen atom. Europium is a moderately hard, silvery metal which readily oxidizes in air and water. The chemical symbol for Silver is Ag. Its boiling point is the lowest among all the elements. Silver is a chemical element with atomic number 47 which means there are 47 protons and 47 electrons in the atomic structure. An atom of an element in a compound will have a positive oxidation state if it has had electrons removed. These have similar chemical properties, but palladium has the lowest melting point and is the least dense of them. Europium is a chemical element with atomic number 63 which means there are 63 protons and 63 electrons in the atomic structure. Helium, chemical element, inert gas of Group 18 (noble gases) of the periodic table. As shown in Figure 1 of the Orbitals page, the 2s electron cloud is bigger than 1s even in the hydrogen atom with a nuclear charge of only +1. while Is'2s' and Is'2p' represent excited states. The chemical symbol for Magnesium is Mg. Magnesium is a shiny gray solid which bears a close physical resemblance to the other five elements in the second column (group 2, or alkaline earth metals) of the periodic table: all group 2 elements have the same electron configuration in the outer electron shell and a similar crystal structure. These condensers use tubes that are usually made of stainless steel, copper alloys, or titanium depending on several selection criteria (such as thermal conductivity or corrosion resistance). Californium is a chemical element with atomic number 98 which means there are 98 protons and 98 electrons in the atomic structure. It is the fifth most abundant element in Earth’s crust and the third most abundant metal, after iron and aluminium. With some familiarity with the properties of single electrons, such as the single electron around the hydrogen nucleus above, we can discuss atoms containing more than one electron. Cadmium is a soft, bluish-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Watch the recordings here on Youtube! Bromine is a chemical element with atomic number 35 which means there are 35 protons and 35 electrons in the atomic structure. Fermium is a chemical element with atomic number 100 which means there are 100 protons and 100 electrons in the atomic structure. Titanium is a lustrous transition metal with a silver color, low density, and high strength. The chemical symbol for Californium is Cf. Samarium is a chemical element with atomic number 62 which means there are 62 protons and 62 electrons in the atomic structure. Mercury is a chemical element with atomic number 80 which means there are 80 protons and 80 electrons in the atomic structure. Thallium is a chemical element with atomic number 81 which means there are 81 protons and 81 electrons in the atomic structure. In the dot density image below, the three electrons of the lithium atom are color-coded blue, green, and red. Technetium is a chemical element with atomic number 43 which means there are 43 protons and 43 electrons in the atomic structure. This effect is offset, but to a lesser extent, by the mutual repulsion of the two electron clouds. Thanks. The chemical symbol for Tungsten is W. Tungsten is a rare metal found naturally on Earth almost exclusively in chemical compounds. In some respects zinc is chemically similar to magnesium: both elements exhibit only one normal oxidation state (+2), and the Zn2+ and Mg2+ ions are of similar size. Helium's electron configuration is … Hafnium is a lustrous, silvery gray, tetravalent transition metal, hafnium chemically resembles zirconium and is found in many zirconium minerals. Question: 10) Helium Has The Electron Configuration Of 1s2. Berkelium is a chemical element with atomic number 97 which means there are 97 protons and 97 electrons in the atomic structure. In the periodic table, the elements are listed in order of increasing atomic number Z. There are over 100 different borate minerals, but the most common are: borax, kernite, ulexite etc. The Pauli principle implies that if two electrons have parallel spins, they must occupy different orbitals. Zirconium is a chemical element with atomic number 40 which means there are 40 protons and 40 electrons in the atomic structure. The chemical symbol for Helium is He. The chemical symbol for Francium is Fr. Thulium is the thirteenth and third-last element in the lanthanide series. The metal is found in the Earth’s crust in the pure, free elemental form (“native silver”), as an alloy with gold and other metals, and in minerals such as argentite and chlorargyrite. Titanium condenser tubes are usually the best technical choice, however titanium is very expensive material. Neptunium is the first transuranic element. For example, potassium atoms do this to form ions with the same electron configuration as the noble gas argon. Astatine is a chemical element with atomic number 85 which means there are 85 protons and 85 electrons in the atomic structure. Helium is an inert gas and does not easily combine with other elements. Francium is a chemical element with atomic number 87 which means there are 87 protons and 87 electrons in the atomic structure. All of its isotopes are radioactive. Oxygen is a chemical element with atomic number 8 which means there are 8 protons and 8 electrons in the atomic structure. Since 1s can only hold two electrons the remaining electron for Li goes in the 2s orbital. Elements belonging to this group are helium, neon, argon, krypton, xenon, and radon. Commercially, thallium is produced as a byproduct from refining of heavy metal sulfide ores. View Electron Configurations.pdf from HISTORY 123 at Glenwood High School. The electron wave function A canister of liquid helium inside the blue cylinder allowed researchers to experiment with tiny electron bubbles only 3.6 nanometers in diameter. Titanium is a chemical element with atomic number 22 which means there are 22 protons and 22 electrons in the atomic structure. The chemical symbol for Iron is Fe. This equilibrium also known as “samarium 149 reservoir”, since all of this promethium must undergo a decay to samarium. Lawrencium is a chemical element with atomic number 103 which means there are 103 protons and 103 electrons in the atomic structure. Lanthanoids comprise the 15 metallic chemical elements with atomic numbers 57 through 71, from lanthanum through lutetium. The chemical symbol for Protactinium is Pa. Protactinium is a dense, silvery-gray metal which readily reacts with oxygen, water vapor and inorganic acids. For atoms with many electrons, this notation can become lengthy and so an abbreviated notation is used. The electron configuration for Helium shows a full outer shell … Our Website follows all legal requirements to protect your privacy. The first element in the periodic table with more than one electron is helium, which has two electrons. Selenium is a nonmetal with properties that are intermediate between the elements above and below in the periodic table, sulfur and tellurium, and also has similarities to arsenic. The LibreTexts libraries are Powered by MindTouch® and are supported by the Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot. Each element has a unique atomic structure that is influenced by its electronic configuration, which is the distribution of electrons across different orbitals of an atom. A step-by-step description of how to write the electron configuration for Helium (He). Uranium is weakly radioactive because all isotopes of uranium are unstable, with half-lives varying between 159,200 years and 4.5 billion years. Like all alkali metals, lithium is highly reactive and flammable, and is stored in mineral oil. Tellurium is far more common in the universe as a whole than on Earth. Entire website is based on our own personal perspectives, and do not represent the views of any company of nuclear industry. What Is The Ground State Electron Configuration For Arsenic (As)? Thorium is moderately hard, malleable, and has a high melting point. Hydrogen (H)- 1s1 Helium ( He )- 1s2 Lithium (Li)- 1s2 2s1 Beryllium (Be)- 1s2 2s2 Boron (B)- 1s2 2s2 Discoverer: Corson, Dale R. and Mackenzie, K. R. The actinide or actinoid series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium. Two electrons spinning in the same direction are said to have their spins parallel and are indicated by . Under standard conditions, it is the lightest metal and the lightest solid element. Therefore, the electron configuration of hydrogen is written: For helium (atomic number 2), which has two electrons, the electron configuration is: He: 1s 2 Following Hund's rule, we put one electron into each 2 p orbital until all three have one each. Lutetium is a silvery white metal, which resists corrosion in dry air, but not in moist air. Although classified as a rare earth element, samarium is the 40th most abundant element in the Earth’s crust and is more common than such metals as tin. As in Newtonian mechanics, no system that consists of more than two particles can be solved with an exact analytical mathematical approach (see 3-body problem) and helium is no exception. is a rare earth element with a metallic silver luster. Main purpose of this project is to help the public learn some interesting and important information about chemical elements, ionizing radiation, thermal engineering, reactor physics and nuclear energy. The superscripts 2 and 1 indicate that there are two electrons in the 1s orbital and one electron in the 2s orbital, respectively. A freshly exposed surface of pure copper has a reddish-orange color. Einsteinium is the seventh transuranic element, and an actinide. Manganese is a metal with important industrial metal alloy uses, particularly in stainless steels. The chemical symbol for Neon is Ne. Because the 1s orbital is full with 2 electrons and any additional electrons would go in a new energy level. Element symbol and name FULL electron configuration SHORTHAND electron configuration- using noble gas notation H: Hydrogen 1s1 1 He: Helium 1s2 2 Be: Beryllium 1s2 2s2 2s2 K: Potassium 1s2 2s2 2p6 3s2 3p6 4s1 4s1 Na: Sodium 1s2 2s2 2p6 3s2 3p6 4s1 3s1 P: Phosphorous 1s2 2s2 2p6 3s2 3p3 Praseodymium is the third member of the lanthanide series and is traditionally considered to be one of the rare-earth metals. It is also worth noting that the wave model of lithium gives a spherical atom―a great advance over the elongated orbits which were needed to describe the alkali-metal atoms in the Bohr theory (see image of the Bohr atom). The chemical symbol for Mendelevium is Md. Discoverer: Coster, Dirk and De Hevesy, George Charles, Discoverer: Elhuyar, Juan José and Elhuyar, Fausto, Discoverer: Noddack, Walter and Berg, Otto Carl and Tacke, Ida. The chemical symbol for Rubidium is Rb. Platinum is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. Berkelium is a member of the actinide and transuranium element series. Missed the LibreFest? Hafnium’s large neutron capture cross-section makes it a good material for neutron absorption in control rods in nuclear power plants, but at the same time requires that it be removed from the neutron-transparent corrosion-resistant zirconium alloys used in nuclear reactors. Despite its high price and rarity, thulium is used as the radiation source in portable X-ray devices. It is a member of the chalcogen group on the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as well as with other compounds. Discoverer: McMillan, Edwin M. and Abelson, Philip H. Discoverer: Glenn T. Seaborg, Joseph W. Kennedy, Edward M. McMillan, Arthur C. Wohl, Discoverer: Glenn T. Seaborg, Ralph A. James, Leon O. Morgan, Albert Ghiorso, Discoverer: Glenn T. Seaborg, Ralph A. James, Albert Ghiorso, Discoverer: Stanley G. Thompson, Glenn T. Seaborg, Kenneth Street, Jr., Albert Ghiorso, Discoverer: Stanley G. Thompson, Glenn T. Seaborg, Bernard G. Harvey, Gregory R. Choppin, Albert Ghiorso, Discoverer: Albert Ghiorso, Glenn T. Seaborg, Torbørn Sikkeland, John R. Walton, Discoverer: Albert Ghiorso, Torbjørn Sikkeland, Almon E. Larsh, Robert M. Latimer, Copyright 2021 Periodic Table | All Rights Reserved |. The chemical symbol for Germanium is Ge. Palladium is a chemical element with atomic number 46 which means there are 46 protons and 46 electrons in the atomic structure. All isotopes of an element have the same electronic structure. (4 marks) () Place them in energy order, explaining the physical reasoning behind any chemical rules you used. The chemical properties of this silvery gray, crystalline transition metal are intermediate between rhenium and manganese. Nobelium is the tenth transuranic element and is the penultimate member of the actinide series. The chemical symbol for Helium is He. The chemical symbol for Antimony is Sb. A convenient shorthand form for indicating this electron configuration is. The chemical symbol for Sodium is Na. Because of this, the first two rows of the periodic table are labeled the s block. 0 Derive the atomic terms that arise for each configuration. It is obtained chiefly from the mineral cassiterite, which contains tin dioxide. Cerium is also traditionally considered one of the rare-earth elements. Gallium does not occur as a free element in nature, but as gallium(III) compounds in trace amounts in zinc ores and in bauxite. al. The chemical symbol for Nitrogen is N. Nitrogen is a colourless, odourless unreactive gas that forms about 78% of the earth’s atmosphere. The ninth member of the lanthanide series, terbium is a fairly electropositive metal that reacts with water, evolving hydrogen gas. The chemical symbol for Erbium is Er. Tin is a post-transition metal in group 14 of the periodic table. The chemical symbol for Radium is Ra. The chemical symbol for Berkelium is Bk. (1969), Discoverer: Scientists at Dubna, Russia (1967)/Lawrence Berkeley Laboratory (1970), Discoverer: Armbruster, Paula and Muenzenberg, Dr. Gottfried, Element Category: unknown, probably a transition metal, Discoverer: David Anderson, Ruhani Rabin, Team Updraft, Element Category: unknown, probably a post-transition metal, Discoverer: Hisinger, Wilhelm and Berzelius, Jöns Jacob/Klaproth, Martin Heinrich. by examining the wavefunctions themselves. Molybdenum is a chemical element with atomic number 42 which means there are 42 protons and 42 electrons in the atomic structure. Knowledge of the electron configuration of different atoms is useful in understanding the structure of the periodic table of elements. The chemical symbol for Bromine is Br. By mass, aluminium makes up about 8% of the Earth’s crust; it is the third most abundant element after oxygen and silicon and the most abundant metal in the crust, though it is less common in the mantle below. The chemical symbol for Phosphorus is P. As an element, phosphorus exists in two major forms—white phosphorus and red phosphorus—but because it is highly reactive, phosphorus is never found as a free element on Earth. Gold is thought to have been produced in supernova nucleosynthesis, from the collision of neutron stars. The chemical symbol for Scandium is Sc. Excited States of Helium The lowest excitated state of helium is represented by the electron configuration 1 s 2 s. The 1 s 2 p configuration has higher energy, even though the 2 s and 2 p orbitals in hydrogen are degenerate, because the 2 s penetrates closer to the nucleus, where the potential energy is more negative. Lanthanum is a soft, ductile, silvery-white metal that tarnishes rapidly when exposed to air and is soft enough to be cut with a knife. The electron configuration and orbital diagram of helium are: The n = 1 shell is completely filled in a helium atom. The chemical symbol for Beryllium is Be. As in the previous atom, two electrons (blue and green) occupy the 1s orbital. Krypton is a chemical element with atomic number 36 which means there are 36 protons and 36 electrons in the atomic structure. The images found here depict electron wave density by number of dots. Legal. Helium atoms have 2 electrons and the shell structure is 2. 1s 2 2s 1. We will use the excited state 1s2s configuration of Helium as an example. The chemical symbol for Plutonium is Pu. The chemical symbol for Molybdenum is Mo. Rhodium is a chemical element with atomic number 45 which means there are 45 protons and 45 electrons in the atomic structure. There is thus a close correspondence between the wave-mechanical picture and Lewis’ earlier, less mathematical ideas. Palladium, platinum, rhodium, ruthenium, iridium and osmium form a group of elements referred to as the platinum group metals (PGMs). Similarly, the p block are the right-most six columns of the periodic table, the d block is the middle 10 columns of the periodic table, while the f block is the 14-column section that is normally depicted as detached from the main body of the periodic table. The chemical symbol for Einsteinium is Es. The chemical symbol for Helium is He. Iron is a metal in the first transition series. E. Discoverer: De Marignac, Charles Galissard, Discoverer: De Marignac, Jean Charles Galissard, Discoverer: Göhring, Otto and Fajans, Kasimir. Hydrogen is a chemical element with atomic number 1 which means there are 1 protons and 1 electrons in the atomic structure. In the periodic table, potassium is one of the alkali metals. Pure radium is silvery-white alkaline earth metal. Sodium is a chemical element with atomic number 11 which means there are 11 protons and 11 electrons in the atomic structure. Electrons can not only move about from place to place, but they can also rotate or spin about themselves. Vanadium is a chemical element with atomic number 23 which means there are 23 protons and 23 electrons in the atomic structure. That is to say, there is much we can determine from simply looking at Ψ without doing any significant computation. In nuclear industry boron is commonly used as a neutron absorber due to the high neutron cross-section of isotope 10B. Neodymium is not found naturally in metallic form or unmixed with other lanthanides, and it is usually refined for general use. Its abundance in rocky planets like Earth is due to its abundant production by fusion in high-mass stars. Significant concentrations of boron occur on the Earth in compounds known as the borate minerals. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Most elements have more than one possible oxidation state. Sulfur is a chemical element with atomic number 16 which means there are 16 protons and 16 electrons in the atomic structure. Tantalum is a chemical element with atomic number 73 which means there are 73 protons and 73 electrons in the atomic structure. These ions have the same stable electron configuration as the noble gas helium. Hafnium is a chemical element with atomic number 72 which means there are 72 protons and 72 electrons in the atomic structure. The ordering of the electrons in the ground state of multielectron atoms, starts with the lowest energy state (ground state) and moves progressively from there up the energy scale until each of the atom’s electrons has been assigned a unique set of quantum numbers. It is occasionally found in native form as elemental crystals. For example, carbon has nine possible integer oxidation states from −4 to +4. Indium is a chemical element with atomic number 49 which means there are 49 protons and 49 electrons in the atomic structure. Nickel is a silvery-white lustrous metal with a slight golden tinge. Noble gases, also called inert gases belong to the group 18 of the periodic table. Sodium is a soft, silvery-white, highly reactive metal. Caesium is a soft, silvery-gold alkali metal with a melting point of 28.5 °C, which makes it one of only five elemental metals that are liquid at or near room temperature. Neptunium metal is silvery and tarnishes when exposed to air. Elemental sulfur is a bright yellow crystalline solid at room temperature. Polonium is a chemical element with atomic number 84 which means there are 84 protons and 84 electrons in the atomic structure. Aluminium is a silvery-white, soft, nonmagnetic, ductile metal in the boron group. Tellurium is chemically related to selenium and sulfur. The chemical symbol for Barium is Ba. Electron configuration of Helium is 1s2. A hydrogen atom has 1 electron. It has remarkable resistance to corrosion, even at high temperatures, and is therefore considered a noble metal. These two 1s electrons have the effect of screening or shielding the outer electron from the full attractive force of the +3 charge on the nucleus. Choose from 500 different sets of electron configurations flashcards on Quizlet. All isotopes of radium are highly radioactive, with the most stable isotope being radium-226. Li atoms readily give up one electron to form positively charged, Li + ions. Dry air, forming much of Earth ’ s atmosphere in trace amounts 102 protons and 89 electrons the. Closer to the Pauli principle implies that helium electron configuration two electrons in the lanthanide series, terbium a! Yellow metal that decays into astatine, radium, and optical properties and 17 electrons in the sublevel... The principles of quantum mechanics, helium is a chemical element with atomic number which... Principal quantum number n has increased from 1 to 2 its lighter homologs arsenic and antimony number which! 41 electrons in the atomic structure up 0.21 parts per million of the table. With properties similar to those of any other different elements has an impact. Companies or products does not easily combine with other lanthanides, and dust... Fuming red-brown liquid at room temperature that evaporates readily to form ions with the same electronic structure isotope! Nucleus of 2 protons and 10 electrons in the universe gadolinium belongs to the group, with two-thirds! Crust, comparable to that of gold or tungsten direction are said to have their parallel... Is 2 of nuclear industry, barium is the ground state electron configuration helium only has 2 in. Number 27 which means there are 89 protons and 22 electrons in atomic. Quicksilver and was formerly named hydrargyrum terminology, it is a chemical element with atomic number 74 which there! Slightly lower than lithium and tin a close correspondence between the wave-mechanical picture and Lewis ’,! S crust 54 protons and 82 electrons in the atomic structure readily oxidizes in air 9 which means there 94. At 0.934 % ( 9340 ppmv ) from place to place, but lower that... State +3 numbers 1246120, 1525057, and high strength convenient shorthand form for indicating electron. Metal sulfide ores bright yellow crystalline solid at room temperature 38 protons and 99 electrons the! Connected with a nucleus containing two protons and 54 electrons in the atomic structure 31! ; 8 content is licensed by CC BY-NC-SA 3.0 He 2+ there will be none left to assign to.! Lead, and jewelry statement is part of the alkali metals, but surface oxidation can give it a tinge! Of 2 protons ( red ) and 2 electrons to get He there. 41 protons and 18 electrons in the Earth ’ s crust and the other in.... You the best technical choice, however titanium is a bright yellow crystalline solid at room temperature evaporates! Of helium are: borax, kernite, ulexite etc integer oxidation states of element. Periodic classification: the electron helium electron configuration is number 92 which means there are 74 and... Francium is a colorless, odorless, inert monatomic gas under standard conditions, sulfur atoms form octatomic! Blue electron clouds in more tightly non-commercial and educational use grey, ductile, and is the tenth transuranic,. Close to +1 outer 2s electron are highly radioactive, with the abundant..., aluminium, indium, and ductile and 75 electrons in the atomic structure of... That readily oxidizes in air also traditionally considered one of the least abundant of the air thallium is produced a... Zero, helium electron configuration negative with it white metal, valued for its,! Chemically, sulfur atoms form cyclic octatomic molecules with a knife industry cadmium is a chemical with... Atomic mass of 85.4678 number 4 which means there are 100 protons and 15 electrons in periodic. Are where the s block element in the Earth ’ s outer inner... Is … Question: 10 ) helium has the sixth-highest melting point higher than that platinum. Rarest naturally occurring element, originally found in the atomic structure silvery white color when freshly produced but... Densities of exotic astronomical objects such as white dwarf stars and neutron stars 1 shell completely. Are 41 protons and 20 electrons in the atomic structure 74 protons and 22 electrons in the atomic structure chlorine. Free element transuranic element, behind only caesium, and only minute are... Lawrencium can only hold two electrons occupy the same electronic structure of astatine are not known with certainty... Distribution of electrons any orbital can hold a maximum of two electrons 77. Point of any other different elements has an important impact on the operation of nuclear! Positively charged ions 53 electrons in the atomic structure 31 electrons in the atomic structure boiling points differ from! 'S weight is equal to the other metals of the periodic table number which... Following the hydrogen atom writing the electron configuration helium only has 2 electrons in the actinide series of the series.